Musical instrument with variable amplitude

ABSTRACT

An electronic organ with tone generators that are coupled to a loudspeaker by depressing key-operated switches, wherein each switch provides a resistance dependent upon the pressure applied to the key so that the musician can control the loudness, attack and decay of a musical note. Each switch includes a highly compressible resistance member whose resistance changes greatly with degree of compression, a first conductor which supports an upper end of the resistance member, and a resilient second conductor normally spaced below the resistance member. Manual depression of a key deflects the lower switch conductor up against the resistance member and compresses it in an amount dependent upon the pressure applied to the key. The fact that the resistance member initially has an extremely high resistance when the first contact touches it, prevents the production of a &#39;&#39;&#39;&#39;popping&#39;&#39;&#39;&#39; sound as the key is depressed.

United States Patent Peterson et al.

154] MUSICAL INSTRUMENT WITH VARIABLE AMPLITUDE [72] Inventors: Robert L. Peterson, Woodland Hills; Paul R. Wieman, Hawthorne, both of Calif. [73] Assignee: Mattel, Inc., Hawthorne, Calif.

[22] Filed: Nov. 2, 1970 [21] Appl. No.: 86,143

[52] US. Cl ..84/1.0l, 84/1.09, 84/1.1, 84/1.27, 84/l.12 [51] lnt.Cl. ..G10h 1/00 [58] Field ofSearch ..84/1.01,1.13, 1.17, 1.18, 84/1.24, 1.26, DIG. 7, 1.27, 1, 423, 424; 200/5 A, 5 R, 159 A, 159 B, 166 C [56] References Cited UNITED STATES PATENTS 1,036,724 8/1912 Rowe ..200/5 A 1,886,284 11/1932 Re26,048 6/1966 2,215,708 9/1940 2,841,044 7/1958 3,564,105 2/1971 2,215,124 9/1940 3,524,375 8/1970 1,780,670 11/1930 2,141,231 12/1938 [151 3,657,459 [451 Apr. 18, 1972 Primary Examiner-Lewis H. Myers Assistant Examiner-U. Weldon AttorneySeymour A. Scholnick [57] ABSTRACT An electronic organ with tone generators that are coupled to a loudspeaker by depressing key-operated switches, wherein each switch provides a resistance dependent upon the pressure applied to the key so that the musician can control the loudness, attack and decay of a musical note. Each switch includes a highly compressible resistance member whose resistance changes greatly with degree of compression, a first conductor which supports an upper end of the resistance member, and a resilient second conductor normally spaced below the resistance member. Manual depression of a key deflects the lower switch conductor up against the resistance member and compresses it in an amount dependent upon the pressure applied to the key. The fact that the resistance member initially has an extremely high resistance when the first contact touches it, prevents the production of a popping sound as the key is depressed.

1 Claim, 4 Drawing Figures Patented April 18, 1972 M/wwrams R056?! 1. PIIIRSd/y P4111 A. 44/71 A? AA} 7 II'TdI/Vi'i BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to musical instruments.

2. Description of the Prior Art One type of electronic organ includes a group of tone generators, each of which can be connected to a common loudspeaker by depressing a corresponding key to close a switch. In some types of organs, oscillator circuits are used which are energized when the switch is closed, and the fact that the oscillations must build up to their maximum value reduces the tendancy of the circuit to create a popping sound as the switch is closed. However, in one type of organ which employs a rotating optical disc with patterns that vary the amount of light to a photocell, and where each key-operated switch serves to connect the photocell to a loudspeaker, a popping sound can occur when the switch is closed. This is due partially to the fact that the photocell creates a signal containing an appreciable DC bias, and that the switch may close at an instant when the AC portion of the signal has a large value.

In organs where a tone signal is coupled to the speaker through a simple key-operated ON-OFF switch, the volume is independent of the pressure applied by the musician to the key, and the musician has limited control over the character of a note. Furthermore, even if the organ is manufactured so that the tones have a noticeable attack or decay, the musician cannot readily adjust the attack or decay for individual notes. In considering the design of apparatus for enabling a musician to control attack, decay and volume, consideration must always be given to the fact that cost must be kept as low as possible in order that the instrument be economical enough to be widely sold.

OBJECTS AND SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic musical instrument of simple and economical construction, which permits close musician control of attack, decay and loudness of musical notes.

Another object is to provide an economical electronic musical instrument of the type which employs tone generators which produce DC bias, which reduces any tendancy to create a pop or other objectionable noise when a key is depressed.

In accordance with one embodiment of the present invention, an organ is provided of a type which has a rotating optical disc for regulating the passage of light from a lamp to a photocell to create tones, and key-operated switches which can be manually depressed to connect the output from any of the photocells to a loudspeaker. Each switch includes a compressible resistance member constructed of a compressible cellular material such as a foam, impregnated with a carbon solution, and a pair of electrical contacts on either side of the resistance member for compressing it. Manual pressure on the key moves one of the contacts towards the resistance member in an amount dependent upon the pressure applied to the key, so the musician can vary the signal strength passing through the switch to the loudspeaker by varying the pressure he applies to the key.

The switch is constructed with a first contact above the resistance member and attached to it so that the resistance member hangs from it. A second of the contacts lies below and spaced from the bottom of the resistance member. When the key is depressed, it moves the lower contact against the bottom of the resistance member, the resistance of the resistance member being initially so great that not enough current can flow to a loudspeaker to create a popping sound. The lower contact member is a resilient member that tends to spring downwardly away from the resistance member when the key is released, the springiness of the lower contact member helping to urge the key towards its initial up position.

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified perspective view of an organ constructed in accordance with the invention;

FIG. 2 is a partial elevation, partial schematic view of the organ of FIG. 1;

FIG. 3 is a partial perspective view of the optical disc of FIG. 2, showing the form of an optical track thereon; and

FIG. 4 is a partial perspective view of the switch portion of the organ of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an electronic organ constructed in accordance with the invention, which has a piano-type keyboard 10 for playing sustained tones and a chord section 12 with keys or buttons for playing chords. Both tones and chords are generated by an optical disc 14 which has many tracks thereon defining the various tones and chords. As shown in FIG. 2, the disc 14 is mounted on a transparent turntable 16. A lamp 18 produces light that passes through a slit 20, through the optical disc and turntable, and into a group of photocells 22. AND TURNTABLE, AND INTO A GROUP OF PHOTOCELLS 00. Each photocell senses the amount of light passing through one optical track on the record, and it generates a current which can pass through a switch 24 to an amplifier 26 that drives a loudspeaker 28. Thus, an electrical signal representing music is produced by the photocells 22 and each sound is converted to an audible signal when a respective switch 24 is closed.

The switch 24 includes a strip of conductive material or conductor 30 on a circuit board 32, and a compressible resistance member 34 whose upper end is attached to the strip conductor 30 by a conductive adhesive 31 or other means that provides a conductive path between the conductor 30 and member 34. A resilient conductor 36 is normally spaced below the bottom of the resistance member 34. The strip or upper conductor 30 is connected to one photocell 22a, while the resilient or lower conductor 36 is coupled through the amplifier 26 to the loudspeaker 28. When the lower conductor 36 is deflected upwardly and contacts the resistance member 34, a conductive path of initially high resistance is provided to allow some current to flow from the photocell 22a to the speaker.

The resistance member 34 is constructed of an easily compressed elastomeric material impregnated with conductive particles, such as a compressible polyurethane foam which has been impregnated with a solution containing carbon particles. A piece of such material undergoes a dramatic change in resistance between a state wherein it is uncompressed or slightly expanded and a state wherein it is highly compressed by the level of force which can be readily applied by a musician s fingers, a typical change being from several megohms to ohms. Although a solid material, such as rubber or polyvinylchloride material impregnated with a conductive material can be used, a foam base material is generally preferable to provide a wide change of resistance throughout a greater distance of compression. A manually operable switch member of key 38 is provided for enabling a musician to deflect the lower conductor 36 and make it contact and compress the resistance member 34. The key has an outer end 40 which is depressed by a musicians finger, a center portion which is pivotally mounted on a bearing 42, and an inner portion 44 which lies beneath the lower conductor 36. A pad 46 is mounted on the top of the inner key end and it constantly contacts the resilient lower conductor.

When a musician depresses the outer end 40 of the key, the lower conductor 36 is deflected and pressed upwardly against the resistance member 34. The greater the depressing force applied by the musician to the outer end 40 of the key, the greater the compression of the resistance member, and therefore the lower resistance therethrough and the louder the signal produced by the loudspeaker 28. A musician can therefore press lightly or hard to produce a soft or loud note, and can apply and remove pressure on the key at various rates to vary the attack and decay of the musical note Accordingly, this arrangement enables close musician control over some of the note characteristics, using a relatively simple switch arrangement.

The switch apparatus is mounted on a frame 48 of the instrument, the pivot 42 being mounted on the frame and a first spacer 50 also being mounted thereon. The resilient lower conductor 36 is mounted on the first spacer 50, and a second spacer 52 is mounted over the lower conductor to space it from the circuit board 32. The resilient member 36 tends to bias the inner end of the key downwardly, but additional spring force is provided by a spring 54 which is mounted on the top of the circuit board 32. Rods 56 project through the spring, circuit board, lower conductor, and spacers, to hold them in alignment with each other, and nuts 58 on the rods hold down the assembly to the frame 48. FIG. 4 is a perspective view showing several switch assemblies, and the form of the various components. As shown in that Figure, the spacers 50, 52 are long strips of insulative material, the lower conductive member 36 is a strip of material with fingers formed therein, and the spring 54 is a long strip of material with bent fingers formed therein. However, individual upper conductors 30 are formed on the circuit board, and individual resistance members 34 and keys 38 are used for the switches.

FIG. 3 illustrates a typical track 60 on the record, which is represented by a transparent line defined by opaque regions on either side of it, the transparent line having many undulations in width. This track 60 defines a sustained musical note or tone of constant volume, the volume produced being dependent upon the switch. When light shines through this track, the photocell receives an AC component representing the sound to be produced plus a DC bias. The DC bias can cause an electrical charge buildup which results in a pop being produced when the switch is first closed. A pop can also be produced if a switch is closed when the AC component is at a high instantaneous magnitude. The popping sound is reduced to a low level when a compressible resistance member 34 of the type shown in FIG. 2 is utilized, which provides a high initial resistance when the switch is first closed. However, some noticeable popping can still occur. This popping sound is further reduced to an unnoticeable level by the use of a resistor 62 of high resistance such as 50 kilohms to drain off any accumulated charge. It may be noted that in previous organs where a simple switch was used which had no appreciable resistance when first closed, a simple bias resistor was insufficient and an active DC bias source was needed to offset the DC bias of the photocell. The photocells displayed different DC biases, so a large number of bias resistors of different values had to be used to offset the biases. The elimination of active DC biases, through the use of the compressible resistance member 34, helps to lower the cost of the musical instrument. The compressible resistance member also reduces popping due to the AC signal components, which could not be reduced even with the use of many bias resistors.

Thus, the invention provides a musical instrument with electronic tone generators in the form of an optical disc that regulates the light to photocells, and relatively simple switches which control the flow of current from the photocells to a loudspeaker (via an amplifier). Each switch has a resistance whose resistance level can be varied by a factor of many times in response to the force applied by a musician to a key, to permit the musician to vary the loudness and attack and decay of musical sounds. This is accomplished by the use of a compressible resistance member whose resistance varies greatly with degree of compression and by the coupling of a manually operated key to conductors that compress the resistance member. The com ressible resistance member is attached to one of the conduc ors, while the other conductor is normally spaced from the compressible resistance member, so that even a low level of sound does not leak through to the loud-speaker. The use of the compressible resistance member with a very high initial resistance, reduces popping that can result from the creation of a DC bias by the photocell, and even this low level of popping can be reduced to a negligible amount by a simple bias'or draining resistor. The compressible resistance member also reduces popping that may be caused by the AC portion of the signal produced by the photocell.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and, consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

We claim:

1. A musical instrument comprising: a plurality of generating means for generating a plurality of electrical signals, each representing a musical sound;

speaker means for producing acoustic sounds of frequencies dependent upon the frequencies of electrical inputs thereto, and of amplitudes dependent upon the amplitudes of the electrical inputs thereto;

a circuit board having a plurality of electrically conductive strips insulated from each other, each of said strips connected to one of said generating means;

a plurality of resistance members constructed of compressible material which undergoes a change in resistance of many times between a highly compressed state and an uncompressed state, each resistance member having a first face attached to one of said strips on said circuit board and a second face;

a sheet electrically conductive spring material coupled to said speaker means, said sheet having a plurality of slots along one edge forming fingers and each finger disposed opposite the second face of a different resistance member; and

a plurality of manually depressible keys for deflecting said fingers against said second faces of said resistance members with forces dependent upon the depressing forces manually applied to the keys. 

1. A musical instrument comprising: a plurality of generating means for generating a plurality of electrical signals, each representing a musical sound; speaker means for producing acoustic sounds of frequencies dependent upon the frequencies of electrical inputs thereto, and of amplitudes dependent upon the amplitudes of the electrical inputs thereto; a circuit board having a plurality of electrically conductive strips insulated from each other, each of said strips connected to one of said generating means; a plurality of resistance members constructed of compressible material which undergoes a change in resistance of many times between a highly compressed state and an uncompressed state, each resistance member having a first face attached tO one of said strips on said circuit board and a second face; a sheet electrically conductive spring material coupled to said speaker means, said sheet having a plurality of slots along one edge forming fingers and each finger disposed opposite the second face of a different resistance member; and a plurality of manually depressible keys for deflecting said fingers against said second faces of said resistance members with forces dependent upon the depressing forces manually applied to the keys. 